118 THE NAUTILUS. 



with Figs. 7, 9 and 11 northern shells. An examination of the 

 youngest shells that I have seen would seem to indicate that 

 lamettidens may be the ancestral form as in very young midti- 

 dentata the teeth are generally fused, so much so in fact that in 

 one of two cases I had separated them as lamellidens; but care- 

 ful focusing of the microscope brought out the fused teeth, and 

 measurements showed the relatively larger umbilicus. 



THE NOMENCLATURE AND SYSTEMATIC POSITIONS OF SOME NORTH 

 AMERICAN FOSSILS AND RECENT MOLLUSKS. II. 



BY JUNIUS HENDERSON. 



Planorbis cirrus White, 1879, from the Tertiary of Wyoming, 

 was the next year cited by the same author as though it were 

 spelled cirrattis. Since then the latter name has been univers- 

 ally, but improperly, used instead of cirrus. 



Physa bullata White, 1886 (U. S. Geol. Surv., Bull. 36), 

 from the Eocene of Utah, is preoccupied by P. bullata P. and 

 M., 1838, and P. bullata Gould, 1855. However, on page 12 

 of hig bulletin, and in the legend of plate 3, White used the 

 name bullattda for the same species, the use of bullata on page 

 22, where it was described, perhaps being unintentional. 

 Hence White's species should be known as Physa bullatula. 

 Whether Gould's species should be renamed depends upon 

 whether it is a valid form or a synonym of some other form, 

 which I am now unable to determine. 



Physa carletoni Meek, 1872, from the Cretaceous of Utah, is 

 incorrectly referred to as P. carltoni by Grabau and Shinier, 

 1900. Such a mistake is easily made, but unfortunately there 

 is a prior use of carltoni in this genus by Lea, 1869. Though 

 confusing, I suppose the names are sufficienty distinct so that 

 Meek's name may stand. His species has been so frequently 

 mentioned in various reports that it would be a shame to dis- 

 turb the name unless required by the rules. 



Ac.ella haldemani White ( = Tortacclla haldemani, in Auricu- 

 lidae), from the Cretaceous of Wyoming, is preoccupied by 

 fji/mnaea haldemani Deshayes, 1867 (Acella haldemani, accord- 



